diff --git a/client.go b/client.go
index 3cadb31..92e38e6 100644
--- a/client.go
+++ b/client.go
@@ -24,7 +24,6 @@ func NewClient(addr string, server string, target string, timeout int, sproto in
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
 	return &Client{
 		id:           r.Intn(math.MaxInt16),
-		r:            r,
 		ipaddr:       ipaddr,
 		addr:         addr,
 		ipaddrServer: ipaddrServer,
@@ -37,8 +36,8 @@ func NewClient(addr string, server string, target string, timeout int, sproto in
 }
 
 type Client struct {
-	id int
-	r  *rand.Rand
+	id       int
+	sequence int
 
 	timeout int
 	sproto  int
@@ -164,7 +163,9 @@ func (p *Client) Accept() error {
 		}
 
 		clientConn.activeTime = now
-		sendICMP(p.id, p.r.Intn(math.MaxInt16), *p.conn, p.ipaddrServer, p.targetAddr, clientConn.id, (uint32)(DATA), bytes[:n], p.sproto, p.rproto)
+		sendICMP(p.id, p.sequence, *p.conn, p.ipaddrServer, p.targetAddr, clientConn.id, (uint32)(DATA), bytes[:n], p.sproto, p.rproto)
+
+		p.sequence++
 
 		p.sendPacket++
 		p.sendPacketSize += (uint64)(n)
@@ -234,11 +235,12 @@ func (p *Client) checkTimeoutConn() {
 }
 
 func (p *Client) ping() {
-	if p.sendPacket == 0 && p.recvPacket == 0 {
+	if p.sendPacket == 0 {
 		now := time.Now()
 		b, _ := now.MarshalBinary()
-		sendICMP(p.id, p.r.Intn(math.MaxInt16), *p.conn, p.ipaddrServer, p.targetAddr, "", (uint32)(PING), b, p.sproto, p.rproto)
-		fmt.Printf("ping %s %s %d %d\n", p.addrServer, now.String(), p.sproto, p.rproto)
+		sendICMP(p.id, p.sequence, *p.conn, p.ipaddrServer, p.targetAddr, "", (uint32)(PING), b, p.sproto, p.rproto)
+		fmt.Printf("ping %s %s %d %d %d %d\n", p.addrServer, now.String(), p.sproto, p.rproto, p.id, p.sequence)
+		p.sequence++
 	}
 }
 
diff --git a/pingtunnel.go b/pingtunnel.go
index 71ee706..fd1c209 100644
--- a/pingtunnel.go
+++ b/pingtunnel.go
@@ -190,6 +190,9 @@ func recvICMP(conn icmp.PacketConn, recv chan<- *Packet) {
 			}
 		}
 
+		echoId := int(binary.BigEndian.Uint16(bytes[4:6]))
+		echoSeq := int(binary.BigEndian.Uint16(bytes[6:8]))
+
 		my := &MyMsg{
 		}
 		my.Unmarshal(bytes[8:n])
@@ -204,7 +207,9 @@ func recvICMP(conn icmp.PacketConn, recv chan<- *Packet) {
 			return
 		}
 
-		recv <- &Packet{msgType: my.TYPE, data: my.Data, id: my.ID, target: my.TARGET, src: srcaddr.(*net.IPAddr), rproto: (int)((int16)(my.RPROTO))}
+		recv <- &Packet{msgType: my.TYPE, data: my.Data, id: my.ID, target: my.TARGET,
+			src: srcaddr.(*net.IPAddr), rproto: (int)((int16)(my.RPROTO)),
+			echoId: echoId, echoSeq: echoSeq}
 	}
 }
 
@@ -215,6 +220,8 @@ type Packet struct {
 	target  string
 	src     *net.IPAddr
 	rproto  int
+	echoId  int
+	echoSeq int
 }
 
 func UniqueId() string {
diff --git a/server.go b/server.go
index f0179af..1ccd7e9 100644
--- a/server.go
+++ b/server.go
@@ -3,25 +3,17 @@ package pingtunnel
 import (
 	"fmt"
 	"golang.org/x/net/icmp"
-	"math"
-	"math/rand"
 	"net"
 	"time"
 )
 
 func NewServer(timeout int) (*Server, error) {
-	r := rand.New(rand.NewSource(time.Now().UnixNano()))
 	return &Server{
-		id:      r.Intn(math.MaxInt16),
-		r:       r,
 		timeout: timeout,
 	}, nil
 }
 
 type Server struct {
-	id int
-	r  *rand.Rand
-
 	timeout int
 
 	conn *icmp.PacketConn
@@ -41,6 +33,8 @@ type ServerConn struct {
 	activeTime   time.Time
 	close        bool
 	rproto       int
+	echoId       int
+	echoSeq      int
 }
 
 func (p *Server) Run() {
@@ -76,8 +70,8 @@ func (p *Server) processPacket(packet *Packet) {
 	if packet.msgType == PING {
 		t := time.Time{}
 		t.UnmarshalBinary(packet.data)
-		fmt.Printf("ping from %s %s %d\n", packet.src.String(), t.String(), packet.rproto)
-		sendICMP(p.id, p.r.Intn(math.MaxInt16), *p.conn, packet.src, "", "", (uint32)(PING), packet.data, packet.rproto, -1)
+		fmt.Printf("ping from %s %s %d %d %d\n", packet.src.String(), t.String(), packet.rproto, packet.echoId, packet.echoSeq)
+		sendICMP(packet.echoId, packet.echoSeq, *p.conn, packet.src, "", "", (uint32)(PING), packet.data, packet.rproto, -1)
 		return
 	}
 
@@ -107,6 +101,8 @@ func (p *Server) processPacket(packet *Packet) {
 	}
 
 	udpConn.activeTime = now
+	udpConn.echoId = packet.echoId
+	udpConn.echoSeq = packet.echoSeq
 
 	_, err := udpConn.conn.Write(packet.data)
 	if err != nil {
@@ -144,7 +140,7 @@ func (p *Server) Recv(conn *ServerConn, id string, src *net.IPAddr) {
 		now := time.Now()
 		conn.activeTime = now
 
-		sendICMP(p.id, p.r.Intn(math.MaxInt16), *p.conn, src, "", id, (uint32)(DATA), bytes[:n], conn.rproto, -1)
+		sendICMP(conn.echoId, conn.echoSeq, *p.conn, src, "", id, (uint32)(DATA), bytes[:n], conn.rproto, -1)
 
 		p.sendPacket++
 		p.sendPacketSize += (uint64)(n)